Multi-channel slot antenna for ultra high frequencies



Feb. 13, 1968 R. w. MASTERS MULTI-CHANNEL SLOT ANTENNA FOR ULTRA HIGHFREQUENCIES Filed March 1, 1965 H II n In an II m IIPUAE if l MMLIEW gEm I/v VENTOR Eoberi ZUagne lilasiers 4 MYM ayz' s United States Patent()filice 33mm Patented Feb. 13, was

3,369,244 MULTI-CHANNEL SLOT ANTENNA FOR ULTRA HIGH FREQUENCIES RobertWayne Masters, Falls Church Va., assignor, by

mesne assignments, to Melpar, Inc., Falls Church, Va.,

a corporation of Delaware Filed Mar. 1, 1965, Ser. No. 435,864 8 Claims.(Cl. 343-771) This invention relates to radio antennas for ultra highfrequencies, particularly antennas intended for radio and televisionbroadcasting.

One object of the present invention is to provide a new and improvedarray of antennas capable of simultaneously serving several televisionor radio stations operating on different frequency channels.

A further object is to provide such a new and improved antenna array inwhich the radiation patterns for all of the frequency channels aresubstantially the same, and in which all of the radiation patterns arenearly circular with only minor variations, so that power is effectivelyradiated in all directions.

Another object is to provide such a new and improved antenna array inwhich there is only a negligible amount of interference or cross-talkbetween the various channels.

A further object is to provide such a new and improved antenna arraywhich is structurally sound and is well adapted for erection on a hightower or on top of a high building.

A further object is to provide such a new and improved antenna arraywhich has a configuration and overall dimensions such as to present noserious structural problems.

Another object is to provide such a new and improved antenna array whichis reasonably easy to construct and low in cost.

Further objects and advantages of the present invention will appear fromthe following description, taken with the accompanying drawings, inwhich:

FIG. 1 is a perspective view of an antenna array to be described as anillustrative embodiment of the present invention.

FIG. 2 is a fragmentary enlarged elevational view of a portion of thearray of FIG. 1.

FIG. 3 is a longitudinal section taken the line 3-3 in FIG. 2.

FIG. 4 is a horizontal section, taken generally along the line 4-4 inFIG. 2.

FIG. 1 illustrates an antenna array capable of serving several ultrahigh frequency television stations simultaneously. The array may bemounted in the highest and best available location. For example, theantenna array may be mounted on a high tower on top of the highestavailable building in a metropolitan area. In this way, all of thetelevision stations may benefit from the advantageous location of theantenna array. Moreover, substantial economies may be effected byservicing several television stations simultaneously.

The illustrated antenna array 10 comprises a plurality of antennas inthe form of parallel elongated wave guides 12 which are verticallydisposed. Virtually any reasonable number of wave guides may be employedso as to service any desired number of television stations. By way ofexample, the illustrated antenna array 10 comprises six parallel waveguides 12, capable of serving six television stations on different ultrahigh frequency channels. Energy is fed to each of the wave guides 12 byan individual transmission facility 14, whereby the transmitter of eachtelevision station is connected to the associated wave guide. As shown,the transmission facilities generally along 14 are in the form ofcoaxial transmission lines or cables connected to the respective waveguides 12.

Each of the illustrated wave guides 12 is in the form of a hollowvertical duct, made of metal so as to be electrically conductive. Thecross-sectional shape of the wave guides may be varied, but it isadvantageous to employ a rectangular cross section, as illustrated tobest advantage in FIGS. 1 and 4. Thus, each of the illustrated waveguides 12 has a pair of opposite parallel sides 16 which are relativelywide or broad, and a pair of relatively narrow sides 18 extendingbetween the broader sides 16.

As shown, all of the wave guides 12 are mounted in a single horizontalrow, edge to edge, with the narrow sides or edges 18 adjacent eachother. The broader sides 16 extend in the direction of the row. On eachside of the array, the broader sides 16 of the wave guides 12 aresubstantially coplanar. As shown, the adjacent narrow sides 18 aresecured directly together, but in some cases it may be desirable tospace them apart and to interpose structural stiffening or reinforcingmembers therebetween.

Rounded vertical members 20 may be mounted at both ends of the row ofwave guides 12 to reinforce the antenna array and to improve theaerodynamic character istics of the array so that it will withstand eventhe strongest winds. The members 20 may be made adequately stiff andstrong structurally. Moreover, it will be understood that cables, strutsand other structural reinforcing members may be employed within, betweenor adjacent the wave guides 12 as needed.

In order to provide for radiation of energy at ultra high frequencies,each of the wave guides 12 is provided with a plurality of radiatingslots 22 which are formed in both of the broader sides 16. The slotsextend longitudinally along the wave guide and are longitudinally spacedin a row along the length thereof. By varying the shape, size andspacing of the slots 22, each wave guide 12 is tuned to a differentfrequency channel. As shown by way of example in FIGS. 1 and 2, theslots 22 in the various wave guides 12 are of different lengths. A highQ or factor of merit is readily obtained, so that the tuning may bequite sharp. In this way each wave guide rejects or sharply attenuatesthe signals received from the other wave guides so that the cross-talkor interference between the various wave guides is negligible.

Another factor which effectively suppresses cross-talk between thevarious wave guides 12 resides in the substantially different spacingsof the radiating slots 22 from antenna to antenna. Since no two of thewave guide antennas will have anywhere near the same effective phaseprogression rate along their axial apertures in any of their operatingbands, the antennas will be inherently too far out of step phasewisewith respect to one another to function to any significant extent aswave couplers in the fields of the adjacent antennas. This is especiallytrue for electric-ally long antennas. Thus, the illustrated antennashave several radiating slots and are several wave lengths long. Thefrequencies of the wave guide antennas should be staggered with respectto antenna location in the array so that the various adjacent antennasare as widely separated as possible in frequency. Such staggeringeffectively reduces the coupling between the adjacent antennas. Toachieve the ultimate suppression of cross-talk, rejection filters may beemployed at the antenna inputs but it is believed that such rejectionfilters will seldom be necessary in actual practice.

As shown, each of the slots 22 has a shape resembling a dumbbell. Thus,each slot has a relatively narrow parallel sided main portion 24 whichconnects with enlarged generally circular end portions 26. Various othershapes 3 may be employed, but the illustrated shape is particularlyadvantageous because it provides a higher Q than normally exhibited by asimple parallel sided slot of resonant length.

The illustrated slots 22 are located centrally on the wave guides 12 sothat the slots extend along the center lines of the broader sides 16.This construction is advantageous to provide desirable radiationpatterns which are nearly circular. However, the central location of theslots 22 mitigates against radiation of energy from the slots. To insureeffective radiation of the ultra high frequency energy from the waveguides, each slot 22 should be provided with a probe or coupler 28,whereby the slot is coupled to the fields within the wave guides. Asshown in FIGS. 3 and 4, each of the illustrated couplers 28 is in theform of an adjustable conductive probe extending into the wave guidefrom the wall 16. The probe 28 is located on one side of the slot 22adjacent the center thereof. Each of the illustrated probes 28 is in theform of an adjusting screw which is tapped into the wall 16 of the waveguide so that the probe may readily be adjusted. Each of the couplingscrews or probes 28 may be adjusted by turning the screw so as to Varythe extent to which the screw projects into the wave guide. Each of theopposite slots 22 in the wave guides should have its own coupling screwor probe 28. The probes 28 for the opposite slots 22 should normally beopposite each other, as shown in FIGS. 3 and 4. The probes for thevarious wave guides may be on either side of the slots 22, as requiredto obtain the desired radiation patterns.

The slots 22 on both sides of each wave guide 12 produce a radiationpattern which is very nearly circular, with only very minor lobes orvariations. Thus, for example, the deviation from a circular pattern maybe as low as 1.5 decibels. It will be evident that each wave guideprovides effective radiation of energy in all directions. Moreover,there is no shadowing of one antenna by another, so that all of the waveguides produce radiation patterns which are substantially the same, withonly minor variations. Accordingly, all of the stations using theantenna array will be effectively served on a virtually equal basis.

The antenna array is readily constructed on a sound structural basis andis well suited for erection on a high tower or other high place.Although the array is relatively long and thin, it may readily beconstructed to withstand the highest winds. The array is reasonablycompact and of modest overall dimensions so that the erection of thearray does not present serious structural problems. For example, theillustrated array for six stations may be 50 feet long, 6 feet wide and6 inches thick, to cite only one possible example.

In short, the antenna array of the present invention will serve quite anumber of ultra high frequency television or radio stationssimultaneously on an efiicient, economical and practical basis. All ofthe stations will be given good radiation patterns which aresubstantially the same, so that substantially equal treatment isaccorded to the stations. The array may be erected at the highest .andbest available location, to the mutual benefit of all of the televisionstations.

Various other modifications, alternative constructions and equivalentsmay be employed without departing from the true spirit and scope of theinvention, as exemplified in the foregoing description and defined inthe following claims.

I claim:

1. In a multi-channel antenna array for ultra high frequencies,

the combination comprising a plurality of wave guides in the form ofmetal ducts of generally rectangular cross section,

each of said wave guides having a pair of oppositely disposed widersides and a pair of opposed narrower sides extending therebetween,

said wave guides being disposed side by side in a row with said narrowersides of the successive wave guides adjacent each other,

said wave guides being disposed with said wider sides of said waveguides in co-planar relation to one another,

each of said wave guides being formed with a series of longitudinalradiating slots in both of said wider sides thereof,

each of said wave guides being tuned to a different frequency channel,

and means for feeding ultra high frequency energy to said wave guides,said wave guides being effective to radiate ultra high frequency energyin the different frequency channels without interference with oneanother.

2. In a multi-channel antenna for ultra high frequencies,

the combination comprising a plurality of elongated parallel wave guidesin the form of hollow ducts having a pair of opposed relatively widesides and a pair of relatively narrow edges extending therebetween,

said wave guides being disposed edge to edge in a row with saidrelatively wide sides extending along the row,

each of said wave guides having a series of spaced longitudinal slotsformed in both of said relatively wide sides,

- each of said Wave guides being tuned to a different frequency channel,

and energy transmission means connected to each of said wave guides,

said wave guides being effective as antennas at the different frequencychannels without interference with one another.

3. In a multi-channel antenna for ultra high frequencies,

the combination comprising a plurality of hollow elongated wave guides,

each of said wave guides being generally rectangular in cross sectionand having a pair of relatively broad sides opposite each other and apair of relatively narrow sides extending between said broad sides,

said wave guides being arranged parallel to one another and in a singlelinear row,

said narrow sides of adjacent wave guides being together while saidbroad sides of said wave guides extend along said row,

each of said wave guides having a series of radiating slots formed inboth of said broad sides thereof for radiating ultra high frequencyenergy,

said slots extending longitudinally and being spaced apartlongitudinally,

each of said wave guides being tuned to a different frequency channel,

and a plurality of means connected to said wave guides for transmittingultra high frequency energy thereto,

said wave guides being effective to radiate energy at the differentfrequency channels without interference with one another.

4. In a multi-channel antenna for ultra high frequencies,

the combination comprising a plurality of parallel elongated wave guidesof generally rectangular cross section,

each of said wave guides having a pair of opposed relatively broad sidesand a pair of relatively narrow sides extending therebetween,

said wave guides being disposed in a linear row with said broad sidesextending along the row,

the adjacent wave guides in said row being secured together with thenarrow sides thereof adjacent each other,

each of said wave guides having a plurality of longitudinal slots formedin both of said broad sides for radiating ultra high frequency energy,

said slots being centrally disposed and spaced tudinally,

each of said wave guides being tuned to a different frequency channel,

and means for supplying ultra high frequency energy at differentfrequencies to said wave guides,

said wave guides being effective to radiate the ultra high frequencyenergy without interference with one another.

5. In an antenna array for a plurality of ultra high frequency channels,

the combination comprising a plurality of hollow elongated wave guidesdisposed parallel to one another and in a row,

each of said wave guides having a pair of broad sides opposite eachother and extending along the row,

each of said wave guides having a series of longitudinally spacedradiating slots formed in both of said broad sides,

each of said wave guides being tuned to a different frequency channel,

and energy transmission means connected to each of said wave guides,

said wave guides being effective as antennas at the different frequencychannels without interference with one another.

6. In an antenna array for a plurality of ultra high frequency channels,

the combination comprising a plurality of hollow elongated wave guidesdisposed parallel to one another and in a row,

each of said wave guides having a pair of broad sides opposite eachother and extending along the row,

each of said wave guides having a series of centrally disposedlongitudinally spaced radiating slots formed in both of said broadsides,

each of said wave guides being tuned to a different frequency channel,

each wave guide having a coupling device adjacent each slot for couplingthe slot to the fields within the Wave guide so that energy will beradiated by the slot,

and energy transmission means connected to each of said wave guides tosupply ultra high frequency energy thereto,

said wave guides being effective as antennas at the different frequencychannels Without interference With one another.

7. In an antenna array for a plurality of ultra high frequency channels,

longithe combination comprising a plurality of hollow elongated waveguides disposed parallel to one another and in a row,

each of said wave guides having a pair of broad sides opposite eachother and extending along the row,

each of said wave guides having a series of centrally disposedlongitudinally spaced radiating slots formed in both of said broadsides,

each of said wave guides being tuned to a different frequency channel,

each wave guide having a coupling probe projecting into the wave guideadjacent each slot for coupling the slot to the fields within the guideso that the slot will radiate energy from the guide,

and energy transmission means connected to each of said wave guides tosupply ultra high frequency energy thereto,

said Wave guides being effective as antennas at the different frequencychannels without interference with one another.

8. In an antenna array for a plurality of ultra high frequency channels,

the combination comprising a plurality of hollow elongated wave guidesdisposed parallel to one another and in a row,

each of said wave guides having a pair of broad sides opposite eachother and extending along the row,

each of said wave guides having a series of centrally disposedlongitudinally spaced radiating slots formed in both of said broadsides,

each of said wave guides being tuned to a different frequency channel,

each wave guide having a coupling probe projecting into the wave guideadjacent each slot for coupling the slot to the fields within the guideso that the slot will radiate energy from the guide,

said probe having means for adjusting the extent to which the probeprojects into the guide,

and energy transmission means connected to each of said wave guides tosupply ultra high frequency energy thereto,

said wave guides being effective as antennas at the different frequencychannels without interference with one another.

No references cited.

ELI LIEBERMAN, Primary Examiner.

1. IN A MULTI-CHANNEL ANTENNA ARRAY FOR ULTRA HIGH FREQUENCIES, THECOMBINATION COMPRISING A PLURALITY OF WAVE GUIDES IN THE FORM OF METALDUCTS OF GENERALLY RECTANGULAR CROSS SECTION, EACH OF SAID WAVE GUIDESHAVING A PAIR OF OPPOSITELY DISPOSED WIDER SIDES AND A PAIR OF OPPOSEDNARROWER SIDES EXTENDING THEREBETWEEN, SAID WAVE GUIDES BEING DISPOSEDSIDE BY SIDE IN A ROW WITH SAID NARROWER SIDES OF THE SUCCESSIVE WAVEGUIDES ADJACENT EACH OTHER, SAID WAVE GUIDES BEING DISPOSED WITH SAIDWIDER SIDES OF SAID WAVE GUIDES IN CO-PLANAR RELATION TO ONE ANOTHER,EACH OF SAID WAVE GUIDES BEING FORMED WITH A SERIES OF LONGITUDINALRADIATING SLOTS IN BOTH OF SAID WIDER SIDES THEREOF, EACH OF SAID WAVEGUIDES BEING TUNED TO A DIFFERENT FREQUENCY CHANNEL,